1. Technical Field
The present invention relates to an inflatable vehicle occupant protection device, and particularly to an inflator which provides inflation fluid for inflating the protection device and to a method of assembling the inflator.
2. Description of the Prior Art
Inflators which provide inflation fluid for inflating inflatable vehicle occupant protection devices, such as air bags, are known. One type of air bag inflator includes a container which holds an inflation fluid under pressure. The container has an opening through which the inflation fluid can flow to inflate an air bag. A rupturable closure is welded to the container and extends across the opening to block fluid flow through the opening. The weld is continuous and forms a fluid seal around the opening.
The weld not only forms a seal but bears the load of the pressure of the inflation fluid acting on the closure. In one type of inflator, the pressure in the container is increased by various known ways to rupture the closure and start the flow of inflation fluid. The pressure at which the closure ruptures could vary considerably from one inflator to another. This variation in pressure required to rupture the closure can be attributed to, among other factors, a variation in the strength of a "heat affected area" of the closure. The heat affected area is an area of the closure heated during the welding operation. The heat affected area is located adjacent the weld. The heat affected area of the closure may be weaker than other areas of the closure, and thus the heat affected area may rupture first to start the flow of inflation fluid through the opening in the container. The size and strength of the heat affected area varies due to a variation in the amount of heat applied to the closure during the welding operation.
If the container is one-piece, the closure is typically welded to an exterior surface of the container. Pressure of the inflation fluid in the container could act directly on the heat affected area to rupture the closure at the heat affected area. If the closure is supported by an interior surface of the container, the heat affected area is at least partially supported by a surface of the container surrounding the opening. This may permit the closure to rupture in a more consistent manner. However, such a container is typically made of at least two pieces and requires additional operations and cost to manufacture and assemble.